1. Field of the Invention
The invention relates to a radiation-curable alkoxy silanized hyperbranched polyester acrylate and a preparation method thereof.
2. Description of the Prior Art
EP 0,953,000 reported a prepolymer obtained by the copolymerization of a multifunctional acrylate, an amine-terminated silane coupling agent, and an unsaturated acid. The prepolymer has a linear molecular structure, with a number average molecular weight up to 3,000 g/mole, and is radiation-curable so that it can be used as a coating for packaging.
WO 03,076,546 reported an adhesive comprised of a flexible polymer (e.g. a polyurethane), a silane coupling agent, a titanate or zirconate, and an anhydrous organic acid, which is exclusively used as adhesive for the fixation of glass windows of automobiles. The adhesive has a high adhesion to glass and good weathering properties; however, the resulting cured film is not clear due to the utilization of inorganic fillers. Therefore, the adhesive can be used only for the inside of a substrate but not the surfaces of the substrate.
The silicon-oxygen-carbon group on the structure of the silane coupling agent may be condensed with a hydroxyl in the presence of a small amount of water, for example, in moisture; therefore, it can be used in various polar substrates as an adhesion promoter. Common silane coupling agents are typically low molecular weight monomers for use as coating additives. To improve its compatibility with coatings, functionalities reactive with the components of the coatings are generally introduced into the molecular structure of the silane coupling agents. It has been a hot topic of conducting studies for obtaining functionalized silane coupling agents by means of chemical modifications for more extensive applications.
Hitherto, many patents and documents concerning the use of silane coupling agents in various coatings have been published. Also, there are many publications reporting that silane coupling agents can be used as radiation-curable coatings when they are acrylated or methacrylated and followed by being mixed with an acrylate resin or a methacrylate resin together. However, it has never been reported to employ a hyperbranched polymer as a backbone for preparing a multifunctional, macromolecular alkoxy silanized hyperbranched polyester acrylate with a high functionality and containing both an alkoxy silicon structure and an acrylate structure.
Based on extensive studies, the inventors have found that the radiation-curable alkoxy silanized hyperbranched polyester acrylate prepared by a new preparation method has not only radiation-curable acrylate groups, but also alkoxy silicon groups that can be condensed in moisture, thereby providing the advantages of a higher curing rate, a low film shrinkage, a high adhesion to substrates, and a good thermal stability, which would overcome the above-mentioned problems encountered in the prior art.